Modified chevron osteotomy for the treatment of hallux valgus with unison bioabsorbable screws: Biomechanical research and clinical applications

Researchers have modified PLA materials to enhance their mechanical properties and meet the clinical requirements. However, the strength and stiffness of PLA are still significantly lower than those of metals. Building on the established chevron clinical procedure and considering the mechanical characteristics of PLA screws, we devised a modified chevron osteotomy (MCO) based on a load-reducing structure with the aim of reducing the load on the screws. Subsequently, in vitro quasi-static in situ compression and dynamic fatigue tests were conducted for both procedures. DIC, micro-CT, and SEM were used to elucidate the unloading effects and structural damage of different bone cutting and implant locations on the PLA bone screws, providing biomechanical data for clinical applications. In-vitro simulation studies indicated that the unloading structure of the MCO procedure reduced the load borne by the PLA screws. Within the load range of the first metatarsal during walking, the MCO procedure exhibited a compressive strength 2.5 times that of the traditional chevron osteotomy groups and even exceeded the titanium alloy screw groups by 25%, ensuring PLA screw fixation strength and stability that are not inferior to metallic materials. A stable load-reducing structure in osteotomy procedures is the key to PLA materials becoming viable alternatives to metal orthopedic fixation devices.